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Energy Supply Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Five reasons why ATP is a good energy source:

A

1 - releases small, manageable amounts so no wastage.
2 - small, soluble thus easily transported.
3 - easily broken down thus energy easily released.
4 - can transfer energy onto another molecule by transferring one of its phosphate groups.
5 - can’t pass out of the cell so cell always has an immediate supply of energy.

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2
Q

Coenzyme

A

Molecule that aids the function of an enzyme, by transferring chemical groups from one molecule to another.

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3
Q

Coenzymes used in photosynthesis, and how:

A

NADP (transfers Hydrogen)

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4
Q

Coenzymes used in respiration, and how:

A
  • NAD (transfers Hydrogen)
  • FAD (transfers Hydrogen)
  • Coenzyme A/CoA (transfers Acetate)
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5
Q

The Light-Dependent Reaction of Photosynthesis occurs in the:

A

Thylakoid membranes

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6
Q

What happens during the Light-Dependent reaction of photosynthesis?

A

Light energy is absorbed by photosynthetic pigments and turned into chemical energy:

ADP + Pi –> ATP
NADP -(reduction)-> NADPH
Water -(photolysis/oxidation)-> O2 + H+

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7
Q

What is the Light-Independent Reaction also known as?

A

The Calvin Cycle

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8
Q

Whereabouts does the Light-Independent Reaction occur?

A

Stroma

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9
Q

With what process is ATP produced in the Light-Dependent Reaction?

A

Photophosphorylation (cyclic and non cyclic)

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10
Q

What are the products of Non-cyclic Photophosphorylation?

A

ATP, NADPH and O2

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11
Q

Briefly describe the four stages of Non-cyclic Photophosphorylation:

A

1 - Light excites electrons in chlorophyll
2 - Photolysis of water
3 - Energy from excited electrons used to produce ATP
4 - This progress reduces NADP

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12
Q

What happens when light excites the electrons in Chlorophyll during Non-cyclic Phosphorylation?

A

Light energy is absorbed by Photosystem II, moving the electrons to a higher energy level. They then move along the Electron Transport Chain to Photosystem I.

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13
Q

What is the main purpose for photolysis in Non-cyclic Photophosphorylation?

A

To replace the excited electrons that leave the chlorophyll from Photosystem II.

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14
Q

How is the energy from the excited electrons in Non-cyclic Photophosphorylation used to produce ATP?

A
  • Excited electrons lose energy as they move along the Electron Transport Chain.
  • This energy is used to transport H+ into the thylakoid, creating an electrochemical proton gradient across the membrane.
  • Protons move down their concentration gradient into the stroma via ATP synthase (CHEMIOSMOSIS)
  • Energy from this movement combines ADP + Pi to form ATP.
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15
Q

Which photosystems does Cyclic Photophosphorylation utilise?

A

Only Photosystem I

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16
Q

Why is Cyclic Photophosphorylation ‘cyclic’?

A

Electrons from the chlorophyll are not passed onto NADP, rather are passed back to Photosystem I via electron carriers.

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17
Q

What are the products of Cyclic Photophosphorylation?

A

Small amounts of ATP only.

No NADPH or O2

18
Q

What are the requirements and overall process of the Calvin Cycle?

A

Requires H+ and ATP to keep turning.

Makes Triose Phosphate from Carbon Dioxide and Ribulose Biphosphate, via the phosphorylation and reduction of Glycerate 3-Phosphate, which can be phosphorylated back to RuBP.

19
Q

How does CO2 and RuBP become GP?

A

Via the formation of an unstable 6-carbon compound which splits into 2 x 3C GP, with a Ribulose Biphosphate Carboxyase (Rubisco) catalyst.

20
Q

How much TP is used to form useful compounds? What happens to the rest?

A

1/6 is used to form compounds. The rest (5/6) is used to regenerate RuBP, using the remainder of the ATP from the Light Dependent Reaction.

21
Q

What is TP converted to and how?

A
  • Hexose sugars, by joining two TPs together.
  • Lipids by using glycerol from TP and fatty acids from GP.
  • Proteins, using some amino acids formed from GP.
22
Q

How many times must the Calvin Cycle turn to produce one Hexose sugar, and why?

A

6 times.

  • 6 turns = 12 molecules of TP.
  • 1/6 TP used to make compounds.
  • 2 x TP needed to produce a Hexose sugar. 12/6 = 2.
23
Q

What is needed from the Light Dependent Reaction to produce one Hexose sugar from the Calvin Cycle?

A

18 x ATP

12 x NADPH

24
Q

What is the optimum light conditions for photosynthesis?

A

High light intensity of a certain wavelength

i.e. blue and red; Chlorophyll a & b and Carotene

25
Q

What is the optimum temperature for photosynthesis, and why?

A

Around 25°C.

Too high and enzymes will denature (Rubisco and ATP synthase)
Too high and stomata will close to prevent water loss.

26
Q

What is the optimum CO2 concentration for photosynthesis, and why?

A

[CO2] around 4%.

Any higher and stomata will close.

27
Q

What is the importance of water abundance in photosynthesis?

A

Too little and photosynthesis stops (no photolysis).

Too much and soil becomes waterlogged (causing a reduced uptake of Mg. Mg is needed to make chlorophyll a)

28
Q

Four stages of aerobic respiration and where they occur:

A

1 - Glycolysis (in the cytosol/cytoplasm)
2 - Link Reaction (in the mitochondria)
3 - Krebs Cycle (in the mitochondria)
4 - Oxidative Phosphorylation (in the mitochondria)

29
Q

What is the purpose of glycolysis?

A

To convert one glucose into 2 x pyruvate (with a net gain of 2 x ATP)

30
Q

Whereabouts does glycolysis take place?

A

Cytosol/cytoplasm

31
Q

When does glycolysis take place and why?

A

In anaerobic and aerobic respiration, because the process requires no oxygen.

32
Q

List the steps of glycolysis:

A

1 - 2 ATPs are used to phosphorylate glucose into 2 triose phosphate molecules (releasing 2 ADP)

2 - Each triose phosphate is oxidised (by NAD) into 2 pyruvate molecules, releasing 4 ATP.

33
Q

List the steps of the Link Reaction:

A

1 - Pyruvate is decarboxylated (releasing 1 CO2)
2 - NAD is reduced from the oxidation of pyruvate to acetate.
3 - Acetate is combined with coenzyme A to form acetyl coenzyme A (Acetyl CoA)

34
Q

What are the products of the Link Reaction and what happens to them?

A
  • 2 x Acetyl CoA to the Krebs Cycle
  • 2 x CO2 released as a waste product
  • 2 x NADH for Oxidative Phosphorylation
35
Q

What happens during anaerobic respiration?

A

Glycolysis, then instead of the Link Reaction, Pyruvate is reduced into ethanol (in plants and yeast) or lactate (in animal cells and some bacteria).

36
Q

What is the purpose of anaerobic respiration?

A

It regenerates NAD so that glycolysis can continue when little oxygen is present, so that some biological process can continue.

37
Q

Outline the three main steps of the Krebs cycle:

A

1 - Acetyl CoA is combined with oxaloacetate to form citrate and CoA (back to Link Reaction)

2 - Citrate is formed into a 5-carbon intermediate by decarboxylation and dehydrogenation.

3 - The 5-carbon molecule is decarboxylated and dehydrogenated thrice (1FADH, 2NADH), then formed back into oxaloacetate by substrate-level phosphorylation.

38
Q

The products of the Krebs Cycle and their uses:

A
  • 1 x CoA for use in the next Link Reaction
  • 1 x Oxaloacetate regenerated for next Krebs Cycle
  • 2 x CO2 released as waste
  • 1 x ATP used for energy
  • 3 x NADH for use in oxidative phosphorylation
  • 1 x FADH for use in oxidative phosphorylation
39
Q

Explain oxidative phosphorylation:

A
  • Hydrogen from oxidised NADH & FADH is split into H+ and e-.
  • Electrons travel down the Electron Transport Chain, losing energy at each carrier which is used by the the carriers to pump H+ from the mitochondrial matrix into the intermembrane space, building an electrochemical gradient across the membrane.
  • H+ moves down its electrochemical gradient (chemiosmosis) via ATP synthase driving the synthesis of ATP from ADP + Pi.
  • In the matrix, at the end of the transport chain, protons, electrons and oxygen (from blood) combine to form water.
40
Q

What is the final electron acceptor in the Electron Transport Chain for respiration?

A

Oxygen

41
Q

How many ATP molecules are formed from one glucose molecule?

A

32

Biology (5 decks)

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